The present invention pertains to a bearing shell for ball-and-socket joints or ball sleeve joints with an inner hollow spherically designed bearing surface and an outer, cylindrically designed support surface, with which the bearing shell can be inserted into a joint housing.
Bearing shells of this type are used in a very great number of variants in ball-and-socket joints and ball sleeve joints. Such joints usually have a ball shaft, which has a ball section at the end in the case of ball-and-socket joints and in the middle in the case of ball sleeve joints, and this ball section is accommodated in the hollow spherical bearing surface of the bearing shell, so that the ball shaft can perform pivoting and rotating movements in relation to the central longitudinal axis of the joint. The bearing shells are in turn usually accommodated in cylindrical holes of a joint housing. The manufacture of the bearing shells of this class, which are usually manufactured from plastic, especially POM, is carried out according to the injection molding technology, and the injection mold is designed as a two-part mold with an inner spherical core and an outer hollow mold adapted to the outer shape of the bearing shell. The inner spherical mold part is separated from the finished bearing shell by forced mold release after the injection molding operation, while the prior-art bearing shells are subject to relatively great deformations. To make these deformations possible, the bearing shells therefore have a plurality of slots which extend axially in the direction of the central longitudinal axis and reach approximately the equatorial plane of the hollow spherically designed bearing inner surface. These slots facilitate the forced release of the bearing shell from the mold, but the selection of the material of a bearing shell that can be removed from the mold by forced mold release is limited as a consequence of the necessary great expansion and the low modulus of elasticity. The limitation of the material selection has in turn adverse effects on the loadability of the bearing shell and consequently of the entire ball-and-socket joint or ball sleeve joint at high temperatures and high loads, because the material of the bearing shell tends to flow in extreme situations, and there is a possibility of migration of the shell material, especially in the area of the slots. This may possibly result in a change in the geometry of the hollow spherical bearing surface with a resulting increase in wear and even complete failure of the ball-and-socket joint or ball sleeve joint affected.
The object of the present invention is therefore to provide a bearing shell of this type which has increased loadability and service life based on an expanded selection of available materials, while the conventional manufacture shall continue to be able to be carried out according to the injection molding technology.
According to the present invention, the bearing shell is designed as a multipart shell comprising at least two shell parts, which can be detachably coupled with one another by a clamping device, wherein the parting plane between the shell parts extends in the direction of the central longitudinal axis of the bearing shell.
Due to the measure according to the present invention, the previously one-part bearing shell of this type can be composed of a plurality, preferably two half shells during the assembly of the ball-and-socket joint or ball sleeve joint. The half shells are manufactured in the conventional manner according to the injection molding technology, but the shell material does not need to have special elastic properties during the removal of the half shells from the mold. It is therefore also possible to use harder and consequently more wear-resistant plastics for the bearing shells compared with the state of the art. In addition, the load limit of the bearing shells according to the present invention is correspondingly increased due to the fact that the slots are not present because forced mold release is no longer necessary.
It proved to be particularly advantageous to design the clamping device such that it comprises at least one pin projecting beyond the particular parting surface of the shell parts and at least one corresponding recess arranged in the respective adjoining shell part. The dimensions of the pin and the recess can be coordinated with one another such that predefined clamping forces or frictional forces can be obtained during the assembly of the shell parts without problems. If the connection of the bearing shell parts is to be designed as a positive-locking connection rather than as a frictionally engaged connection, this can be achieved without problems by means of a suitable locking connection at the pins and in the recesses.
Corresponding to another advantageous embodiment of the subject of the present invention, the cylindrically designed support surface on the outside of the bearing shell is provided with a plurality of recesses arranged in the circumferential direction. These recesses lead to a rather substantial reduction in the weight of the bearing shell.
In addition, it may be advantageous to provide the inner hollow spherical bearing surface with at least two grooves extending in the direction of the central longitudinal axis for receiving lubricant. The grooves provided as a lubricant reservoir additionally contribute to the increase in the load possibilities and service lives of the ball-and-socket joints or ball sleeve joints, in addition to the corresponding material selection.
Moreover, it proved to be advantageous to select the thickness of the bearing shell to be constant in the area of the hollow spherical bearing surface, which additionally contributes to a uniform state of load of the bearing shell.